1. Field of the Invention
The present invention relates to a ball implanting method and, more particularly, to a method for implanting solder balls on a substrate of an integrated circuit.
2. Description of the Related Art
A conventional ball implanting machine for an integrated circuit in accordance with the prior art shown in FIGS. 1-14 comprises a suction fixture 10, an evacuating device 20, two pivoting and inverting devices 24, a ball carrier 30, and a substrate 40. The suction fixture 10 is initially located above the evacuating device 20. The suction fixture 10 is provided with a plurality of ball grooves 11 and a plurality of through holes 12. Each of the through holes 12 of the suction fixture 10 is connected to a respective one of the ball grooves 11. The evacuating device 20 is combined with the suction fixture 10. The evacuating device 20 is provided with a vacuum chamber 21, a plurality of connecting holes 22, and an air hole 23. Each of the connecting holes 22 of the evacuating device 20 is connected between a respective one of the through holes 12 of the suction fixture 10 and the vacuum chamber 21. The vacuum chamber 21 of the evacuating device 20 is connected between each of the connecting holes 22 and the air hole 23. The air hole 23 of the evacuating device 20 draws air outward from the vacuum chamber 21 or introduces ambient air into the vacuum chamber 21. The pivoting and inverting devices 24 are mounted on two opposite sides of the evacuating device 20 to pivot and invert the suction fixture 10 and the evacuating device 20. The ball carrier 30 is movably mounted on the suction fixture 10. The ball carrier 30 contains a plurality of solder balls 1. The substrate 40 is located under the evacuating device 20. The substrate 40 is provided with a plurality of soldering pastes 41.
In operation, the ball carrier 30 is moved on the suction fixture 10 reciprocally as shown in FIGS. 2 and 3 to introduce each of the solder balls 1 into the respective ball groove 11 of the suction fixture 10. Then, the evacuating device 20 draws air in the vacuum chamber 21 of the evacuating device 20 outward through the air hole 23 of the evacuating device 20 as shown in FIG. 4 to produce a vacuum suction force in the vacuum chamber 21 of the evacuating device 20 so as to suck each of the solder balls 1. Then, the pivoting and inverting devices 24 invert the suction fixture 10 through one hundred and eighty degrees (180°) so that the suction fixture 10 is located under the evacuating device 20 and faces the substrate 40, and each of the solder balls 1 faces downward and aligns with a respective one of the soldering pastes 41 of the substrate 40 as shown in FIG. 5. Then, the substrate 40 is moved upward toward the suction fixture 10 to rest each of the soldering pastes 41 on the respective solder ball 1 as shown in FIG. 6. Then, the evacuating device 20 introduces ambient air through the air hole 23 into the vacuum chamber 21 as shown in FIGS. 7 and 7a to release each of the solder balls 1 so that each of the solder balls 1 falls down and is implanted in the respective soldering paste 41 of the substrate 40. Finally, the substrate 40 is moved downward to space from the suction fixture 10 to detach the solder balls 1 from the suction fixture 10 as shown in FIG. 8, thereby accomplishing the ball implanting process.
As shown in FIGS. 9 and 10, when each of the ball grooves 11 of the suction fixture 10 has a smaller depth, each of the solder balls 1 largely protrudes outward from the respective ball groove 11 of the suction fixture 10, so that the solder balls 1 will interfere with and squeeze each other, thereby causing some of the solder balls 1 missing the respective ball groove 11 of the suction fixture 10. In addition, when each of the ball grooves 11 of the suction fixture 10 has a smaller depth, one of the solder balls 1 is jammed between two adjacent solder balls 1 as shown in FIG. 11, and its upper half will be scraped, scratched or cut during movement of the ball carrier 30 as shown in FIG. 12.
On the contrary, when each of the ball grooves 11 of the suction fixture 10 has a greater depth, each of the solder balls 1 is fully hidden in the respective ball groove 11 of the suction fixture 10 as shown in FIGS. 7 and 7a. Thus, when the substrate 40 is too close to the suction fixture 10, each of the soldering pastes 41 is easily stuck to the suction fixture 10, so that when the substrate 40 is spaced from the suction fixture 10, each of the soldering pastes 41 is left in the respective ball groove 11 of the suction fixture 10 as shown in FIG. 8. Alternatively, when the substrate 40 is too far from the suction fixture 10 as shown in FIG. 13, each of the solder balls 1 is easily deflected from the respective soldering paste 41 when falling down, so that each of the solder balls 1 is not combined with the respective soldering paste 41 solidly and closely as shown in FIG. 14.